The present invention relates to an array substrate of a thin film transistor liquid crystal display (TFT-LCD) and a method of manufacturing the same.
Image-sticking is one of the problems to be solved in connection with image quality of a thin film transistor liquid crystal display (TFT-LCD). A TFT-LCD displays a frame of image in a retention mode. If a same image is displayed for a long time, the liquid crystal molecules of being driven may be polarized, such that the orientation of the liquid crystal molecules cannot be controlled with a signal voltage any more. In this case, even when the screen is switched to a next image, the last image is still weakly displayed on screen. This phenomenon is called as “image-sticking.” For example, when a typical checker pattern is displayed for a long time and the screen is switched to another image, for example, grey-scale image, it is found that the checker pattern is still displayed partially on screen. This is the image-sticking problem.
Current research shows that image-sticking is related to materials of an alignment layer. The image displayed for a long time as described above causes charge accumulation on alignment layers or other energy-storing microstructure on both sides of the liquid crystal layer, generating an additional voltage difference between pixel electrodes, i.e., a certain DC bias voltage. Thus, when a data signal of a different image is applied, the liquid crystal molecules are aligned similarly and generate partially a same optical rotation effect as that in the previous image. Current solution to solve the problem of image-sticking is material diversification and process development.
FIG. 6 is a schematic view showing a conventional TFT-LCD array substrate. FIG. 7 is a schematic view showing an equivalent circuit of the conventional array substrate. The conventional pixel structure comprises a first thin film transistor 2, a gate line 3, a pixel electrode 4, a pixel electrode 5 in a next row, a data line 6, a common electrode 7, and a second thin film transistor 8. On the array substrate, a plurality of gate lines parallel to each other intersect a plurality of data lines parallel to each other to define a plurality of pixel region arranged in a matrix. The first thin film transistor 2 is disposed between the gate line 3 and the pixel electrode 4 in a corresponding row to control charging and discharging of the pixel electrode 4 and display images. The second thin film transistor 8 is provided between the gate line 3 and the pixel electrode 5 in the next row. A source electrode of the second thin film transistor 8 is connected with the common electrode 7 in the next row, and a drain electrode of the second thin film transistor 8 is connected with the pixel electrode 5. In operation, when a scan signal for the present row is applied, the signal on the gate line 3 controls the common electrode 7 to be connected with the pixel electrode 5 in the next row such that charges accumulated on the pixel electrode 5 in the next row is discharged; when a scan signal for the next row is applied, there is no charge accumulated on the pixel electrode 5 in the next row, thereby reducing the image-sticking phenomenon.
However, in this conventional technology, as shown in FIG. 6, the second thin film transistor 8 occupies a portion of the pixel electrode 5 in the next row, decreasing the aperture ratio and deteriorating image quality of the TFT-LCD, such as brightness and contrast ratio.